“I think his views would be disastrous,” the New York congressman said on MSNBC’s “Morning Joe.” “I think he appeals to the lowest common denominator. This is an isolationist wing from the 1930s.”

King, who has been harshly critical of his Republican colleague in the past, said Paul’s rhetoric “is just feeding into paranoia.”

( QUIZ: Do you know Rand Paul?)

“Rand Paul brings it to this hysterical level,” King said. “He talks about the CIA trying to kill Americans having coffee in Starbucks, when he talked about President Obama listening to his cell phone conversations.”

“That to me is just feeding into paranoia,” he added. “We do need an intelligent debate, and I don’t think Rand Paul is capable of having that debate.”

His comments follow a growing backlash this week from the right against Paul’s stance on foreign policy.

( WATCH: Peter King slams Rand Paul: ‘Feeding into paranoia’)

While noting that the GOP benefits from a figure like Paul, who doesn’t fit the typical Republican mold, conservative columnist Rich Lowry wrote Tuesday in National Review that the Kentucky senator and potential 2016 candidate’s “instincts sometimes seem more appropriate to a dorm-room bull session than the Situation Room.” Lowry also writes for POLITICO.

Bret Stephens similarly took Paul to task in the editorial pages of The Wall Street Journal on Monday, writing Paul is not qualified to be president.

“What we need as the Republican nominee in 2016 is a man of more glaring disqualifications. Someone so nakedly unacceptable to the overwhelming majority of sane Americans that only the GOP could think of nominating him,” Stephens wrote. “This man is Rand Paul.”

Paul took to the opinion pages himself in The Washington Post on Tuesday to push back against his critics and defend his stance on Iran.

“False choices between being everywhere all of the time and nowhere any of the time are fodder for debate on Sunday morning shows or newspaper columns,” Paul wrote. “Real foreign policy is made in the middle; with nuance; in the gray area of diplomacy, engagement and reluctantly, if necessary, military action.”